Hi Thomas, On Saturday 13 September 2014 21:12:16 Thomas Gleixner wrote: > On Sat, 13 Sep 2014, Laurent Pinchart wrote: > > The TWL RTC interrupt is a double-nested threaded interrupt, handled > > through the TWL SIH (Secondary Interrupt Handler) and PIH (Primary > > Interrupt Handler). > > > > When the system is woken up from suspend by a TWL RTC alarm interrupt, > > the TWL PIH and SIH are enabled first (due to the normal IRQ enabling > > sequence for the PIH and to the IRQF_EARLY_RESUME flag for the SIH) > > before the TWL RTC interrupt gets enabled. This results on the interrupt > > being processed by the TWL primary interrupt handler, forwarded to the > > nested SIH, and then marked as pending for the RTC by handle_nested_irq > > called from the SIH. > > > > The RTC interrupt then eventually gets reenabled the kernel, which will > > try to call its top half interrupt handler. As the interrupt is a nested > > threaded IRQ, its primary handler has been set to the > > irq_nested_primary_handler function, which is never supposed to be > > called and generates a WARN_ON, without waking the IRQ thread up. > > > > Fix this by setting the IRQF_EARLY_RESUME for the TWL RTC interrupt to > > ensure it gets enabled before the parent handlers try to process it. > > > > This is likely a bit of a hack, I have a feeling that a more generic > > solution that would fix the problem for all nested threaded IRQs enabled > > as a wake up source by enable_irq_wake would be better. > > Indeed. It's a hack. This is not the first abuse of IRQF_EARLY_RESUME > which is used to "fix" ordering issues with nested thread handlers. > > I haven't come around yet to analyze the issue and come up with a proper > core side mechanism to handle that case. I put it on the "look at it while > trapped in a tin can" list.
Should this patch be applied in the meantime, or do you think you will be trapped in a tin can in the not too distant future ? -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
